To answer your question “why do they get behind guys like Mike Brown instead of REAL honest black folk murdered by police?” Because the left knows the truth is that the system generally DOES work and a bad white cop that murders an innocent black man will likely be convicted. They NEED a case where the “evil cop” will “get away with murder” in order to create more outrage (and thus more fundraising and more street violence). So they pick cases where the black guy is in the wrong so that they will get the outcome they want that advances the narrative that the system is rigged against black folk.